Jig saw



July 2'1, 1953 w. L. GASKELL 1 646,089

JIG SAW Filed April 50, 1947 2 shets-sheet 1 z j V '//z a AA 738 f/' //5 20 Y //z 7l j! d; l 76 lo 44 a 4 il /Ad E fi . j az INVENToR.

'' E Y Miter j.. cia/fell July 21, 1953 w. L. GAsKELL 2,646,089

.11G sAw Filed April 3o, 1947 2 Sheets sheet 2 INVENTOR. Mli" A. cias/fell.

Patented July 2l, 19553 JIG SAW Walter L. Gaskell, Ypsilanti, Mich., assignor to King-Seeley Corporation, Ann Arbor, Mich.

Application April 30, 1947, Serial No. 744,950

This invention relates broadly to new and useful improvements in jig saws.

An important object of the invention is to pro vide a jig saw having walking beams which carry the saw blade.

Another object of the invention is to provide theV walking beams with novel pivot supports which assure a relatively quiet and essentially frictionless operation.

Another object of the invention is to provide a novel means rfor tensioning the saw blade.

Still another object of the invention is to provide means for maintaining a substantially uniform tension on the saw blade at all times during operation of the machine.

Yet another object ofthe invention is to provide novel mountings for the walking beams which greatly reduce the destructive effect of inertia on the saw blade when the beams reverse their direction of travel.

A further object of the invention is to provide a novel chuck assembly for fastening the saw blade to the walking beams.

A still further object of the invention is to provide novel pull-rod assemblies for the chucks.

Ayet further object of the invention is to provide a pull-rod assembly which is uniquely constructed to translate rocking movement of the walking .beams to reciprocatory movement of the pull rods with maximum efciency and minimiun no1se.

Another object of the invention is to provide a pull-rod assembly of the above-mentioned character which includes novel means for holding the saw blade against rotation and facing properly into the work at all times during operation of the machine.

Still another object of the invention is to provide a novel back-up or guide for the saw blade, which guide is capable of performing its intended function without causing portions of the blade to crystallize in the manner of metal guides conventionally used.

Yet `another object of the invention is to provide novel means for blowing sawdust and the like away from the saw blade.

A further object of the invention is to provide a drive means for the walking beams which is associated therewith in such manner as to assure a smooth, noiseless, and eiicient transfer of motion from the drive means to the walking beams.

A still further object of the invention is to provide a novel and improved mounting for fastening the arm portion to the base portion of the supporting framework.

3 Claims. (Cl. 143-70) Other objects and advantages of the invention will be apparent during the course of the following description.

In the drawing, forming a part of this specification and wherein like numerals are employed to designate like parts throughout the same,

Fig. l isa side elevational View of a jig saw embodying the invention, parts thereof being broken away and shown in section for clearness of illustration;

Fig. 2 is a front elevational view of the saw;

Fig. 3 is an enlarged, vertical, transverse sectional view taken on the line 3-3 of Fig. l;

Fig. 4 is an enlarged view of the portion of Fig. 1 enclosed in the circle 4;

Fig. 5 is an enlarged, fragmentary, vertical, longitudinal sectional view taken on the line 5-5 of Fig. 2;

Fig. 6 is an enlarged, fragmentary, vertical, transverse sectional View taken on the line 6-'6 of Fig. l;

Fig. 7 is an enlarged view of the portion of Fig. 5 enclosed in the circle l;

Fig. 8 is a vertical, sectional View taken on the line 8-8 of Fig. 7 and Fig. 9 is a transverse, horizontal sectional view taken on the line 9-9 of Fig. 8.

The main supporting frame of the jig saw shown in the drawing by way o-f illustration is made in two parts. One part is an elongated hollow base I0 and the other part is a generally L- shaped hollow arm I2, which is mounted on and fastened to the base. The downwardly extending portion I4 of the arm I2 fastens onto the rear of the base l0 and the horizontal portion I6 of the arm extends forwardly above and substantially parallel to the base.

A walking beam I8 in the horizontal arm portion I6 is r-ockably mounted on a fixed upstanding pivot support 20 (Fig. 1), and a corresponding walking beam 22 in the base Ill-is rockably suspended from a xed depending supporting pivot 24. Both walking beams I8 and 22 extend substantially the full length of the frame portions I6 and IIJ in which they are mounted, and the forward ends thereof are attached to pull rods 26, which rods are mounted in and guided for vertical reciprocatory movement by supporting cages 30. On the proximate ends of pull rods 26 lare chuck assemblies 32 which clamp opposite terminal portions of a saw blade 35.

As best shown in Fig. 1, the rearward ends of walking beams I8 and 22 are joined by a connecting rod 36 which extends vertically through the arm portion. I4 and holds the attached ends of the beams in fixed spaced relation to tension the saw blade 313. Also, it will be observed that the upper walking beam IS is formed with a rearward extension 353 which is connected to an eccentric drive lill by a second connecting rod 12. This rod d2 is contained in the vertical arm portion ifi behind connecting rod 3S. The eccentric drive it@ is carried by the inner end of a horizontal driving spindle lli which is journaled for rotation in one side wall of the base It. The outer end of driving spindle lli carries a pulley il@ which is adapted to be driven by an electric motor or other suitable power source through an endless belt (not shown), according to conventional practice.

Ihe jig saw is provided with a wcrktable 158 having a central opening 5@ through which the saw blade 3d extends. This table d8 and its mounting are conventional and need not be described in detail; however, a general description is givenin order that the operation and construction of the saw may be fully understood. As best shown in Fig. 5, the table i3 surmounts and is fastened to front and rear trunnions 52 and 54 by cap screws 56, and the trunnions are pivotally attached to a trunnion support eof conventional design. The latter is fastened( solidly to the base iii by machine screws Stand the trunnions 52 and 551 are held in a selected adjusted position by a locking handle 62 in the conventional manner. When locking handle S2 is loosened, the table [i3 can be adjusted to the desired angle, and the locking handle 62 can then be tightened to hold the table in the selectedadjusted position. A pointer Se fastened to and extending forwardly of the trunnion support 58 cooperates with a suitable scale S6 on the front trunnion 52 (Fig. 2) to indicate visibly the position of table 48.

In its general operation, the jig saw is similar to conventional machines of this type. Any suitable drive means capable of rotating pulley i5 within the range 500 to 105i) R. P. IVI. is satisfactory. Pulley (i5 drives the eccentric i9 which, in turn, acts `through connecting rod l2 to oscillate or rock walking beams i8 andilabout their respective pivot supports 2G and 24. Manifestly,

actuation of walking beams i8 and 22 in this manner effects a rapid up-and-down movement or reciprocation of the saw blade 34 in the usual manner.

In a device of this character, it is desirable that the frame be constructed in at least two parts in order to facilitate assembly of the working ele ments. Some vibration inevitably occurs during operation ofthenmachine, and since it originates at or near the end ofthe arm i2, it has a marked tendency to loosen the fastening means which holds the several parts of the frame together. One feature of the present invention resides in the provision of novel means for fastening the arm l2 securely on the base l.

As best shown in Figs. 1 and 4, the arm portion i4 is formed atrthe lower end thereof with an inwardly extending annular flange GS which seats solidly on a correspondingly shaped annular ange TE) of the base B. The latter flange 'i0 is provided with an annular series of holes 'i2 which register with correspondingly located internally threaded openings 'lfiinflange 68, and cap screws 'it extend upwardly through holes l2 into the threaded openings lll. In this connection, it should be observed that the bottom of base it! is open so that access may be had to screws l.

The free ends of the frame members frequently are jarred or otherwise moved. out of alignment by handling and abuse during shipment or in use.

For proper operation of the machine, the pull rods 26 must align accurately. Experience teaches, however, that the average home user of devices of this type does not take the time or trouble either to align the rods properly when the machine is first set up or assembled or to check the rods from time to time thereafter to sec that they remain properly in alignment. According to the present invention provision is made for bringing and holding the two frame members into position to properly align the upper and lower pull rods 26. Moreover, this is accomplished automatically when the arm I2 is fastened on the base i8, thus relievingY the user of responsibility and assuring proper operation of the machine at all times.

I have found that if holes 'l2 and openings 'inl are provided with countersinks 78 and 8% respectively, which countersinks are arranged to open onto the interface between flanges 68 and 'lli and small sleeves or bushings 82 are fitted snugly into the countersinks around cap screws '19, a superior and highly efficient fastening which is capable of withstanding continuous vibration for long periods of time is obtained. Preferably, the bushings 82 are tapered slightly from substantially the middle thereof as best shown in Fig. 4, and they preferably are pressed solidly against the walls of countersinlrs 'i3 and 8i] when screws 1G' are tightened.

By reason of the above construction, the sleeves or bushings 8,2 force the arm l2 into proper position on the base Iii when screws 'it are tightened. Also, bushings 82 relieve kcap screws 'f6 of considera-ble strain, and the only.. function the latter need perform in the combination is to hold flanges 68 and le together.

For a specific and more detailed description of the eccentric drive, attention is directed to Fig. 6. As suggested, the driving spindle 44 extends through a boss Se in onevertical wall of the base iii, and a bushing 8% in the boss supports the spindle for substantially frictionless rotation. The pulley 4S is fastened to drive shaft 44 by a set screw 88 and is separated from boss fifi by a snap ring 90 and washer 92. The eccentric 4() is fastened to the inwardly projecting terminal portion of drive shaft 44 by a set screw 94 and is separated from the inner end of bushing 86 by a washer s. Eccentric 40 is here shown in the form of a crank arm xed on the shaft ifi and carrying a driving pin 9S. Opposite the crank arm, eccentric dil is formed with a relatively large counterbalance mass which assures substantially vibrationless operation. Driving pin 98 carries an eccentric housing lili) which is fastened to the lower end of connecting rod 42 by a coupling m2. A bushing IM mounted in eccentric housing it@ and jcurnaled on pin 98 provides substantially frictionless rotation for the housing. Washer HB6 and snap ring IBB hold the eccentric housing lili) and its bushing IGA removably associated with driving pin 98.

From the foregoing it will be readily apparent that rotary movement of driving pin 98 about the driving spindle da will act through connecting rod 42 to rock the walking beams l and 2?. cn their respective' pivot supports 2l! and 24. However, it also will be apparent that the lower end of connecting rod 42 not only moves up and downto reciprocate walking beams i8 and 22 but it also swings or oscillates back and forth due to the rotary path described by housing |00. The usual practice with this type of drive is to fasten the upper end of connecting rod 42 to the walking beam I8 by a suitable pin and bearing connect'ion which transmits vertical movement of the connecting rod to the walking beam but 4merely rotates to accommodate oscillatory or swinging movement of the rod. However, this conventional type of connection requires frequent oiling to assure smooth operation and to prevent noise. Moreover, in .a machine of this character such a connection wears relatively rapidly and may be the cause of considerable noise and vibration in operation.

Broadly, according to the present invention the connecting rod 42 is fastened to walking beam I 8 f by a flexible, resilient, nonmetallic connection which obviates all of the undesirable results attendant upon the conventional pin and bearing referred to above. The connection is here shown in the form of a grommet or bushing I I0 which is fitted over the upper end of connecting rod 42 and in a suitable opening provided in the walking beam |6. Grommet I I 6 may be made of any suitable resilient material such as rubber or the like and it is fastened securely on the rod by snap rings-'I I2. Also, it will be observed that the grommet Iii] is formed with an annular peripheral groove and provides radially extending portions .above and below the beam, which portions define cushions which bear against the beam and prevent the grommet from canting or wobbling in the beam opening. The inherently resilient grommet ||6 yields or flexes to accommodate swinging or oscillatory movement of connecting rod 42 while simultaneously transmitting vertical movement to the walking'beam |8. There are no parts to oil or lubricateand essentially noiseless operation is assured. Tests have shown this connection to bedurable and eiiicient and in many ways far superior to the conventional pin and bearing connection.

Another feature of the invention` resides in the manner in which .walking beams |8 and 22 are formed and the manner in which they are mounted in the supporting frame. Except for rthe extension 38 the two walking beams `|8 and 22 are identical. As best shown in Fig. 3, each beam comprises a pair of channel members I|4 placed back to back and spot welded or otherwise fastened together. 'I'his construction assures a lightweight, essentially rigid unit which is pre-eminently suited for the intended purpose. When so constructed, the walking beams have low inertia in operation and relieve parts .associated therewith and actuated thereby of considerable strain and stress.

According to the present invention, walking beams I 8 and 22 are fastened to pivot supports 20 and 24 respectively by cap screws- I|6, which `screws extend through grommets I I8 of rubber or the like. These grommets II 8 conveniently may be identical to the grommet I I 0 hereinabove described. Also, it will be readily apparent that the grommets II8 serve the same purpose as grornmet I I8 in so far as pivotal movement of thewalking beams is concerned, since they yield to permit the beams to rock back .and forth on their supports and there is no relative rotative movement between the parts during such action to cause noise or vibration in the machine. As shown in Fig. 3, washers |20 are interposed between the heads of cap screws I I6 and grommets ||8 so that the latter are compressed vbetween pivot supports 28 and 24 and Walking beams I8 Aof the grommets II8 is assured by meta1 sleeves |22 which extend axially therethrough and limit the extent to which they can be compressed. Thus, grommets ||8 will be uniformly compressed in all cases, and skilled workmen are not required to tension the rubber properly in order t-o obtain maximum eiiciency of operation.

Connecting' rod 36 also is fastened to walking beams I8 and 22 by grommets |24 which are identical to grommets ||2. Also, grommets |24 are fastened to the walking beams I8 and 22 in the same manner as grommets I I2.

In addition to providing essentially frictionless and relatively quiet operation, the above construction and arrangement of parts maintains a substantially uniform tension on the saw blade 34 at all times during operation of the machine and greatly mitigates the destructive effect on the blade of inertia which results when the walking beams reverse their direction of travel. Thel particular shape of grommets |I8 and |24 provides pads or cushions above and below the middle webs of walking beams I8 and 22, and the walking beams normally are positioned so that the forward ends thereof must be pulled together slightly in order to fasten the saw blade 34 in place, so that the pads are compressed when the saw blade is inserted in the machine. As a result, the resilient action of the compressed pads acts through the walking beams I8 and 22 to maintain a substantially uniform tension on the saw blade 34. Also, there is a certain amount of resilience in the walking beams I8 and 22 which augment the action of the grommets.

The instant arrangement is particularly ecacious as compared with the conventional construction in jig saws of this type Where the saw blade is tensioned by a spring or springs in such manner that the tension increases as the blade goes down and decreases as the blade goes up. This prior art or conventional construction creates rapid reversal of stresses in the blade which is conducive to early breakage.

In addition to the above, there are several features in the front-end construction of the machine vvhich warrant special consideration. One such featureis the pull-rod assembly which was referred to briefly in the general description. Specically, there is a separate pull-rod assembly as sociated with each walking beam I8 and 22, and since they are substantially identical in construction and operation, a'detailed description of one will suffice.

Each pull-rod' assembly includes a cage 30 which comprises a pair of vertically spaced disk- Vshaped headers |26 integrally connected at diametrically opposed sides thereof by integral vertical Webs |28. The cage 30 is arranged vertically in the assembly and slidably supports the pull rod 26 which extends through central openings |38 in headers |25. Bushings |32 are provided in openings I 38 around push rod 26 to provide an antifriction surface for the rod. As best shown in Fig. 5, push rod 26 also extends through the horizontal web of the Walking beam with which it is associated, and, in order to hold the walking beam longitudinally fixed on the pull rod, washers |34 and pads |36 are fastened on the pull rod at opposite sides of the walking beam by cross pins |38. The pads |36 may be made of any suitably tough resilient material such as rubber or `the like, and a pad is provided at each side of the able toV position the KVholdedown aunts@ end or the walking beam is bifurcated to facilitate assembly oi the pull rod therewith. The rubber pads A absorb the destructive eiect of inertia on the saw blade and by their re llient action convert rocking oroscillatory movement oi the walking bearn into direct reciprocatory7 movement' of the pull rod.

'Oneof the outer washers 131i is generally square in plan and formed with a hub portion which interiits with the coacting'cross pin E38 vto-prevent relativero'tation between the `washer and pull rod 26. The 'square washer i3d fits snugly between the side flanges of the walking beam and consequently engages the inner walls of the flanges to prevent rotation of the pull rod. In this manner, .the saw blade 3d is prevented from rotating and held in proper ass ciation with the work at all times during operation of the machine.

.The lower pull-rod assembly extends betweenr a boss M2 at the top of Vthe base lil and a hori- Zontal annular carrier support ld which is an integral partoi a transverse web (not shown) at or near the bottom of thebase. As clearly shown in the drawing, the carrier idf is formed with an annular seat Hifi which supports the lower header 26. The upper header -i 25 is held rotatably hired in boss if by a projecting pin It which enters a vertical guideway E59. Also7 it will be observed that the upper header l25 is below and in slight spaced relation with the trunnion support 53 and that an annular spring 52 connned between trunnion support 58 and upper header |26 acts against the latter to hold lower header 42e solidly against seat The upper pull-rod assembly is similarly mounted vertically spaced aligned openi es .i554 vand l t'in-thehoriaontal armportion iii, and the vupper header 26 is similarly provided with a .radiallyprojecting pin H58 which enters a vertical gu-ideway it .tohold the assembly against rotation. The lower` header 26 sea-ts downwardly against a swivel 1F52 having a swivel extension ll?.- ywhich Vcarries the usual hold-down foot it. The lswivel Etz and its appurtenances are conventional, :andthe swivel extension itil is vertic adjustioot it@ properly with respect to Athe table d8. However, there is one element associated with the swivel assembly .which is believed -to be novel and a feature of this invention. -Fastened to the swivel extension itil by screw 53 is a saw guide il@ of Micarta which comprises super-posed layers or laminations ot fabric impregnated with a phenol resin. or plastic. It will be observed that the'saw HQ extends downwardly .and forwardly from the screw itil, and the lower or ici-ward end thereof is bifurca'ted to straddle or embrace at least a portion of the saw blade Ell.

In practice, the bifurcation at the end of saw guide El@ may be formed by reversing the saw blade .from Ythe position shown in Fig. 5 and pressing .theguide against the cutting edge of the blade soV that the latter forms a groove therein. When the saw `blade 3d is reversed and vrnounted as shown in thedrawing, the saw cut nts over the rear marginal portion of the bladeand holds the sarne steady during operation of the machine.

To my knowledge, saw guides lhave heretofore been made ofernetal, Vand rubbing between the blade the guide causes the blade to crystallize and become brittle. I have discovered that this undesirable eiect is substantially eliminated when a liiicartaiguideof the type hereinabove-de- .scribed is employed.

A second saw guide H2 identical with the upper Al. il

guide HD is provided immediately below the table 48.

Another feature of importance is the chuck asseinbly 32 which comprises a tubular chuck body IM having'a errule nut Il threaded into one end thereof and a cap H8 over the other end. An adjusting nut l 89 and a set screw 82 are threaded radially into the body llll at diametrically opposed sides thereoic and a chuck shoe (B4 is provided in the lower end oi the assembly between body Htl and cap l'ii. As best shown in Figs. 7 and 8, the pull rod 26 has a flared terminal portion |86 which nts into a correspondingly shaped annular recess in the lower end of nut HB and seats against a radial shoulder i913 in the chuck body I'Efi. When nut i'i is tightened, it holds the pull rod 2t fastened solidly in the chuck assembly.

The saw. blade 3F@ extends into the chuck through an opening E52 in cap H8 to a position between screws i8@ and 82. Also, it will be observed (Fig. 9) that the chuck shoe ISA has a horizontal base portion i913 which bridges the in ternalbore o the chuck body il@ and is non-rotatably received and guided for movement in a shallow groove ie in the end face of body lill. A strip is cut and bent from one end of the base BLl 'to form an upstanding tongue 596 and to denne a longitudinal medial slot it through which the saw blade extends into the body Al lil. As shown in Fig. the u ostanding tongue |98 is interposed between saw blade 3Q and set screw |82, and the inner end o adjusting screw it is formed with suitable teeth or serrations 269 which bite into and grip the saw blade when the set screw is tighten-ed. The outer portions of screws 80 and H2 extend through opening in cap H8 to hold the latter assembled on chuck body i'ifl.

In operation, screw Hildis adjusted to position the saw bla-detti substantially centrally in the opening 92, and set screw 82 is tightened against the chuck shoe Hifi to clamp the saw blade firmly in the` chuck body llll. rhis arrangement provides a simple and highly efficient means ior clamping theesaw blade 34.

Heretoiore, some diiculty has been encountered in that the chuckholding member tends to fracture or break the saw blade when forced thereagainst with suilicient tightness to hold the Asame during operation oi the saw. rl`-his undesirable eiect is'substantially entirely eliminated by thepresent construction. The teeth orserrations "il'bite into the sawV blade to hold the same solidly in the chuck, but the screw i8@ is not rotated 'afterits initial adjustment so that the teeth ZEG do not tend to tear or break the blade. Set screw iSZ is rotated to cla-nip the saw blade 3l! in the chuck, but the upstanding tongue portion |95 oi the chuck shoe i851 serves as a buiier to prevent rotation of the screw from chewing or breaking theblade.

Still another feature of the invention resides in the provision of a cylinder 262 on the horizontal arm portion EG, which cylinder receives a piston 2M- -on the upper end of tubular pull rod 25 and pumpsair under pressure down through the pull rod to the chuck 32 where it is discharged through opening it and along the saw blade 3G to blow away sawdust which accumulates around the saw-cut during operation of the machine. Cylin- -der 252 is fopen at the ybottom only. and in operation, yair is alternately sucked and discharged through lthe hollow pull rod 26 which thus perlforms a dual function fin the combination of pull rod for-the saw 'blade 3d and air passage -ior Vthe pump 262j 264. n this connection vit will be observed that the opening IZ in chuck 32 functions as a nozzle to direct the air downwardly and at both sides of the saw blade 3. Also, it will be observed that the cylinder 204 isfthreaded into the opening |54 and serves to maintain the upper header 26 in place by maintaining downward pressure thereagainst through the medium of an annular spring 266 interposed therebetween.

It is to be understood that the form of the invention herewith shown and described is to .be taken as la preferred example of the same and that various changes in the size, shape and arrangement of parts may be resorted to without departing from the spirit of the invention or the scope of the appended claims.

Having thus described the invention, I claim:

1. In a jig saw having a frame, upper and lower y walking beams generally horizontal and parallel to each other, rubber fulcrums securing intermediate points on the walking beams to the support so that distortion of the fulcrums permits rocking of the beams, la generally vertical link eX- tending between the rear ends of the beams, rubber bodies flexibly securing the ends of the link to the beams, pull rods for the front ends of the beams, rubber bodies exibly securing the pull rods to the beams, and means for rocking the beams on the fulerums.

' .2. The invention set forth in claim 1 wherein said means comprises a rotary eccentric, a connecting rod drivably secured at one end to the eccentric, and a rubber body flexibly securing the other end of the rod to a beam, y

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